Internet providers in Germany I: your options

The (larger) Internet providers (Internetdiensteanbieter in German) in Germany are as follows:

• Deutsche Telekom (picture). It is the national telephone, Internet and mobile telephone provider. It is a big company, the biggest telecommunications company in Europe. 30% of the company is directly/indirectly owned by the German government.
  
• Vodafone/Arcor. It is the second biggest fixed telephone provider in Germany. It was the first company to offer a flat rate service. (I have this provider!)
  
• 1&1. This is a company that belongs to "United Internet", a group of Internet companies (portals, mail providers, online marketing, etc). Claims to have more DSL clients after Deutsche Telekom.
• Strato. Is part of "freenet AG" group of telecommunication companies. Bought some months ago the German Business of Tiscali, the Italian Telecommunications company.
  
• Versatel. A Dutch company sold to Tele2, but the German branch is independent. Looks like it only operates in southern Germany mostly.
• O2. Part of the Spanish own Telefonica group. Known more for the Mobile telephone services. Used to be VIAG Interkom.

These are the ones I have found information about. I will cite more in my next post. It is a bit difficult as there is no much information in English and with my limited German my research is slow. Please read my second post, I will give you the information you must consider when you take your decision of which Internet provider you go for.